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As i was measuring this, the R7020 blew up. I think i might've plugged in the charger wrong because there's no green light. have replaced it with another resister with the same marking "470" but still no green light. What did i do

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R7020 usually gets burnt because of short in U7090, or one of the filter caps from its pin 6.
Seems to be U7090 in this case.
Also check for short, or low value at 3V42 rail; before and after U7090 is removed.

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I don't think that.
Something else happened there.
Unless you used fake charger, which gives full voltage always.
Original Apple Magsafe 2 gives only 3V at the first moment, before the board is detected correctly.
Bench power supply also can generate such kind of problem.